Aqueous foams are generally known.
U.S. Pat. No. 4,683,004 discloses foamable compositions and their use as hair styling mousses and foaming hand lotions and cleansers. The foamable composition comprises water and a foam stabilizer. The foam stabilizer is a non-ionic cellulose ether which is substituted with methyl, hydroxyethyl or hydroxypropyl groups and which further is substituted with a long chain alkyl radical having 10 to 24 carbon atoms. The foamable composition comprises a hydrocarbon propellant.
European patent application EP-A-0 362 655 discloses foamable pharmaceutical compositions which comprise water, a gel forming agent, an effective amount of a drug and a propellant. The gel forming agent preferably is a water-soluble cellulose derivative, such as methylcellulose, or gelatin. The propellant is preferably carbon dioxide and nitrous oxide.
For easy availability of the gas and for environmental reasons, it is desirable to provide aqueous air foams which are useful for various applications, that means foams which are made by physically mixing air into a fluid.
U.S. Pat. No. 5,026,735 relates to the treatment of hazardous material or other substrate with aqueous air foam. The foam is produced from a water-based composition which comprises (a) a water-soluble polyhydroxy polymer, such as guar gum or poly(vinyl alcohol), (b) a polyvalent ionic complexing agent, such as borax, (c) a foaming agent, such as various surfactants, (d) a pH modifier, and (e) water as the main component.
One object of the present invention is to provide new aqueous air foam which is suitable for various uses, such as powder granulation or coating solid particles like tablets.